OBD-II Code · Network
U0401
Invalid Data Received from ECM/PCM
Severity
high
Left alone, this one tends to take other parts with it.
Can you drive it
Not for long
Driving on this one risks further damage. Get it to a shop rather than carrying on with it.
Indicative cost (USD)
$100–$1,500
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
A module received implausible data from the PCM.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Multiple CELs
- Limp mode
Likely causes
- Failing PCMMost common
- Noisy bus
- Wiring
Read the full diagnostic procedureU0401 means a module on the network is receiving data from the ECM/PCM but the data is implausible — wrong format, wrong checksum, out-of-range value…
U0401 means a module on the network is receiving data from the ECM/PCM but the data is implausible — wrong format, wrong checksum, out-of-range values, or a message that fails the consistency check against other broadcast data. This is different from U0100 (no communication) — with U0401, the ECM IS talking on the bus, but what it's saying doesn't make sense to the receiving module.
Symptoms
warning lights, transmission shift issues (TCM rejects ECM torque/RPM data), traction control or ABS disabled, sometimes drivability issues from accessory modules getting bad load data. Cheapest-first ladder: scan all modules and look for paired codes — U0401 alongside U0100 means the ECM is partially down (one bus leg working, the other not); U0401 alone usually means an ECM data corruption issue (failing internal memory, a recent reflash that didn't take cleanly, or a software calibration mismatch after a module swap). Check ECM power and grounds (low voltage causes ECM to send malformed data), then check for any recent module replacements or reflashes — a TCM swapped in without matching its calibration to the ECM is a classic U0401 generator. Measure CAN bus voltages with a scope if available: CAN-H idles around 2.5V and pulses to 3.5V dominant; CAN-L idles around 2.5V and pulses to 1.5V dominant. Marginal bus voltages cause garbled messages that show up as U0401 rather than full U0100 loss. Expensive-misdiagnosis caveat: U0401 is often a software/calibration mismatch, not a hardware failure. Before quoting any module replacement, check OEM TSBs for reflash bulletins and verify all modules are at the correct calibration level. A $0 reflash at the dealer or with J2534 equipment will often clear U0401 that shops have been chasing with parts for weeks.
Vehicle-specific patterns2011-2014 Dodge/Ram with TIPM throws U0401 alongside U0100 when the TIPM internal CAN gateway corrupts messages between buses.
- 2011-2014Dodge/Ram with TIPM throws U0401 alongside U0100 when the TIPM internal CAN gateway corrupts messages between buses.
- 2007-2013GM half-ton trucks throw U0401 frequently after PCM reflashes that weren't followed up with a TCM relearn — both modules need matching calibrations.
- 2003-2007Ford SuperDuty 6.0L throws U0401 from the FICM bus corruption pattern when the FICM is failing — the FICM is between the PCM and the bus and corrupts messages on its way out.
- 2008-2013BMW vehicles throw U0401 after DME (engine module) replacement when the new DME isn't properly coded to the chassis.
- 2007-2012Volvo and Ford-Volvo platforms (S40, V50, C30, Mazda3 share-platform) throw U0401 from a CEM (Central Electronic Module) software corruption that requires a Volvo VIDA reflash.
Estimated repair$0 (reflash/relearn) to $1,200 (module replacement plus dealer programming).
Look up another code
U0401 — frequently asked
What does a U0401 code mean?
A module received implausible data from the PCM.
What causes a U0401 code?
Common causes: Failing PCM; Noisy bus; Wiring.
What are the symptoms of a U0401 code?
Typical symptoms: Multiple CELs; Limp mode.
Is it safe to drive with a U0401 code?
Not for long. Driving on this one risks further damage. Get it to a shop rather than carrying on with it. Estimated repair: $100-$1,500.
How do I diagnose a U0401 code?
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
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